v-xEPA
United States
Environmental Protection
Agency
Health Effects Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S1-81-066 Dec. 1981
Project Summary
Studies in Children
Exposed to Low Levels of Lead
Herbert L. Needleman
Two separate studies were con-
ducted with the overall objective of
examining the impact of lead at low
dose on the neuropsychological func-
tion of children.
In the first study, a sample of children
identified as having elevated lead
levels in the dentine of shed deciduous
teeth (N = 19) were compared to chil-
dren with low dentine lead (N = 22) on
electroencephalograms and a panel of
8 auditory and speech processing
tasks.
Quantitative electroencephalograms
were obtained from 20 sites under 4
conditions in these subjects. The
spectrum from 0.5 - 32 Hz was ex-
amined; four bands were studied
(alpha, beta, delta, and theta) under
four conditions. Of the 320 compari-
sons, 10 differed at P - 0.025 or less
(Wilcoxin-Mann, Whitney two sample
test). These 10 features, nine behav-
ioral measures previously obtained,
and maternal I.Q. were then submitted
to multivariate analysis. A stepwise
linear discriminant function analysis
showed that adding the EEG to behav-
ioral analysis in the model increased
the discriminating power from P =
0.015 to P = 0.001.
The most useful diagnostic features
were EEG slowing (delta) over the
parietal cortex and decreased full
scale I.Q.
Of the 8 speech and auditory out-
comes studied, significant differences
favoring the low lead group were
found on three measures of auditory
processing: (1) Goldman-Fristoe-
Woodcock Auditory Selective Atten-
tion Test, (2) Staggered Spondaic
Word Test (Left noncompeting), (3)
Speech Discrimination.
This Project Summary was devel-
oped by EPA's Health Effects Research
Laboratory, Research Triangle Park,
NC, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
While the toxicity of lead at high dose
is widely acknowledged, considerable
controversy exists as to whether lesser
doses produce adverse health effects.
Lead is known to inhibit certain enzyme
systems at extremely low concentra-
tions. Among those most sensitive are
D-aminolevulinic acid dehydrase,
adenyl cyclase, and ferrochelatase. It is
not, however, universally accepted that
these biochemical changes and other
changes represent adverse health ef-
fects.
For the purposes of the investigations
described below, an adverse health
effect is defined as "an alteration in the
functioning of an organism which di-
minishes its ability to adapt to a chang-
ing environment. As a result, the orga-
nism's longevity, vigor, or reproductive
capacity is reduced." In a changing
environment, the ability to register
change and then make decisions based
upon the data is essential to survival.
The organ in which these executive
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functions primarily reside is the central
nervous system. The organizing princi-
ple of these investigations is that the
child's CNS is a candidate site for the
early expression of adverse effects of
lead exposure. The Lead Exposure
' Program at Children's Hospital Medical
Center has focused on CNS performance.
Earlier studies by the group had reported
that children thought to be undamaged
by lead, but who had elevated dentine
levels, were less able on a number of
measures of CNS function when com-
pared to controls. Among the perform-
ances which appeared sensitive to lead
were verbal intelligence, auditory and
speech processing, attention and class-
room behavior.
This study examines the electrophysi-
ology of the CNS of a subsample of high
and low lead subjects, and also compares
them on a number of other measures of
auditory and speech processing. A
separate sample of children from an-
other city were evaluated by teacher
ratings, family history, and their dentine
lead levels measured. This offered an
opportunity, not only to replicate our
previous observations, but to evaluate
the effects of lead on classroom per-
formance while controlling more com-
pletely for other covariates which could
be confounding.
Conclusions
Study I
Alterations in neuropsychologicfunc-
tion were demonstrated in electroen-
cephalograms of asymptomatic children
with elevated body lead burdens. These
changes tended to be located in midline
brain structures. The addition of EEC
analysis to a battery of psychologic
outcomes sharpened diagnostic pre-
cision remarkably.
Statistically significant decrease in
function was found on three of nineteen
speech processing outcomes. Outcomes
tended to favor low lead subjects gen-
erally. The relatively small sample size
may be responsible for the failure of
certain outcomes to reach statistical
significance.
Study II
Teachers' Behavioral Ratings as a
Function of Lead Burden.
The proportion of negative teachers'
1 reports of classroom behavior tended to
increase with increasing dentine lead
concentrations. The items most sensitive
to lead were distractibility, disorganiza-
tion, ability to follow a sequence of
directions, and overall classroom func-
tioning.
After data reduction by cluster analy-
sis, the cluster containing the items
"distractible" and "disorganized" was
found most sensitive to lead exposure.
The impact of lead was evaluated by
stepwise multiple logistic regression. A
significant (p = 0.013) lead effect was
found, controlling for major covariates.
This study replicated in part a previous
investigation from this laboratory which
shows that teachers' assessments of
classroom behavior are sensitive to lead
exposure. It goes further than that study
by controlling for a number of covariates
that could be related to outcome. The
ability o'f the child to inhibit irrelevant
stimuli is critical to the task of academic
learning. The item "distractible" which
evaluates that ability is consistently
sensitive to lead exposure. It is reason-
able to expect that this deficit is related
to the impaired performance on speech
processing measured here.
Recommendations
These studies add to the weight of
those which report lead effects at low
dose, and demonstrate that the threshold
for appearance of adverse behavioral
effects is a function of the sensitivity of
the methods brought to bear on measur-
ing outcome.
The findings of alterations in EEC,
speech processing, and classroom be-
havior in samples clinically assumed to
be free of frank toxicity supports the
prudence and hygienic utility of reducing
lead in the environment available to
children.
Studies of lead effects in children,
should attend to those behaviors which
are expressions o'f the organism'sability
to focus attention.
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Herbert L. Needleman, formerly with Children's Hospital Medical Center, Boston,
MA, is now with the University of Pittsburgh School of Medicine, Western
Psychiatric Institute and Clinic, Pittsburgh, PA 15261.
Carl Hayes is the EPA Project Officer (see below).
The complete report, entitled "Studies in Children Exposed to Low Levels of
Lead," (Order No. PB 82-108 432; Cost: $8.00, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Health Effects Research Laboratory
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
ff U S GOVERNMENT PRINTING OFFICE, 1981 — 599-017/7409
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